Mobile enclosures such as trailers are used for almost innumerable purposes. A variety of such enclosures, such as mobile homes, tractor trailer rigs, and camping trailers, have evolved to meet various commercial and recreational needs. In many cases, the size of a trailer may be limited by factors such as, for example, laws and regulations limiting the size of vehicles allowed on the highways, the need for a compact storage volume, the limitations imposed by a garage or other structure in which the trailer is to be stored when not in transit, and a desire to minimize wind resistance during transit. However, trailers sized to accommodate these transit and storage considerations may not allow for the quantum of internal volume desired (or even necessary) for the trailer to perform its intended function, such as providing temporary living or work space when not in transit or storage.
Expandable trailers have evolved to overcome this problem. An expandable trailer is one that is repeatedly reconfigurable from a closed configuration to an open configuration. In the closed configuration, the trailer shell has outer dimensions suitable for transit or storage. In the open configuration, portions of the trailer are reconfigured to provide an expandable enclosure adjacent and connected to the trailer shell. Thus, in the open configuration, the trailer shell and expandable enclosure together provide the desired quantity of internal volume available for work and/or living space.
A common expandable trailer concept might be thought of as the box-within-a-shell concept. Under this concept, the expandable enclosure comprises a box having multiple sides which are permanently connected to each other. In the closed configuration the box is positioned within the shell, which minimizes the trailer's overall dimensions for transit or storage. When additional internal volume is needed, the box is moved out of the shell, usually in a direction lateral to the trailer's length.
One disadvantage associated with this concept is the amount of volume required to store the box within the shell in the closed position. The volume required may be so great, for example, that the trailer shell might not be usable at all when in the closed position. Moreover, this arrangement leads to inflexibility and interference difficulties with respect to the placement of items such as cabling, air conditioning ducts, appliances, and any other type of hardware mounted within the interior space of the shell. Additionally, because multiple panels (ceiling, floor, sides) forming the box are permanently joined together, the deployment mechanism must be able to move the weight of the entire box in and out of the shells. This often requires the use of devices such as rack and pinion mechanisms, which may jam if not in perfect alignment.
Another expandable trailer concept involves the placement of various hinged panels on or in the shell that can be pivoted into their various positions such as the ceiling, floor, side walls, and outermost wall of the expandable enclosure. A common problem with this concept is that the outermost wall of the expandable enclosure cannot be attached directly to the shell, unlike the other panels forming the expandable enclosure.
For example, in U.S. Pat. No. 5,106,142, issued to Hegedus, a panel must first be rotated into its ceiling position of the expandable enclosure, carrying the outermost wall with it as it moves, and only after the ceiling is in position can the outermost wall then pivot down or roll out from the ceiling panel. In addition, the hinged nature of the panel impairs its ability to to form a tight seal with the shell when the trailer is in its closed configuration. Another folding panel approach is shown in U.S. Pat. No. 2,181,844, issued to Winters. Winters does not have an outermost wall per se. Instead two arcuate sections are pivoted outward from inside the shell, and then panels stored within these sections are telescoped from their ends until they meet each other. At this point, the two arcuate sections form one continuous arcuate section that serves the same purpose as the side walls and outermost wall found on a box-like expandable enclosure. A disadvantage of the Winters approach is the amount of shell volume occupied by the two arcuate positions when in the stored or closed position, leading to many of the same difficulties as with the box-within-a-shell concept. A second disadvantage is that, where structural walls are required, separate sets of structural walls are required for the shell and for the expandable section, thus resulting in potential duplication of relatively heavy and large structural wall members.